1. Field of Invention
Embodiments of the present invention relate to an acidic gas absorbing agent, a method for removing an acidic gas, and an apparatus for removing an acidic gas.
2. Background Art
A greenhouse effect through an increase in concentration of carbon dioxide (CO2) has recently been pointed out as a cause of a global warning phenomenon, and an urgent task is to implement an international environment protection measure on a global scale. The emission of CO2 is mainly derived from industrial activity, and a momentum towards the suppression of CO2 emission to environment has been increased.
Techniques for the suppression of an increase in the concentration of acidic gases including CO2 include the development of energy saving products, techniques for the utilization of acidic gases as resources and isolation and storage of acidic gases, conversion to alternative energy such as natural energy and nuclear energy that do not emit acidic gases. Techniques for the separation and recovery of acidic gases being emitted are known as one of such techniques.
Acidic gas separation techniques studied up to now include absorption, adsorption, membrane separation, and cryogenic separation methods. Among them, the absorption method is suitable for massive and efficient treatment of gases and is under studies on application to plants and power generation stations.
A method in which exhaust gases that emit in combustion of fossil fuels (for example, coal, petroleum, and natural gas) are brought into contact with a chemical absorbing agent to remove and collect CO2 contained in the combustion exhaust gas, and a method that stores the collected CO2 are known as methods that are mainly intended, for example, for thermal power stations using fossil fuels. Further, a method in which acidic gases such as hydrogen sulfide (H2S) other than CO2 are removed using chemical absorbing agents has been proposed.
In general, alkanolamines exemplified by monoethanolamine (MEA) have been developed as chemical absorbing agents used in the absorbing method since 1930s and have also currently been used. This method is cost-effective and, further, an increase in size of removing apparatuses is easy.
Alkanolamines used in the absorbing method include 2-amino-2-methylpropanolamine, methylaminoethanol, ethylaminoethanol, propylaminoethanol, diethanolamine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, and dimethylamino-1-methylethanol.
When these amines are used solely, the CO2 absorption rate is not satisfactory and, thus, in some case, these amines are usually used in combination with compounds having a reaction acceleration effect. Cyclodiamines are known as compounds having a reaction acceleration effect but suffer from a problem of a high tendency towards diffusion due to high vapor pressure. The use of amino acid salts sometimes improve the diffusibility. As long as the present inventor knows, CO2 absorbing properties are not satisfactory.
Thus, the development of novel reaction accelerators that have excellent CO2 absorbing properties and improved diffusibility has been demanded.